At the Frontier / Lab's Electron Beam Also Aimed at Industrial Uses

By Earl Lane, Washington BureauNovember 16, 1999

While the Jefferson Lab was built as a place for basic research on the atom's core, it already has been returning some more practical dividends.

In designing the centerpiece of the lab - an accelerator that produces a continuous, hair-thin beam of electrons - the researchers decided to use superchilled, resistance-free accelerating cavities to more efficiently boost the electrons in the beam to nearly the speed of light.

They quickly realized that the superconducting cavities through which the beam was accelerated also could be adapted to serve as drivers for a powerful free-electron laser.

The resulting device recently became the first free-electron laser to produce a record 1,720 watts of continuous power - or about 1.7 million times more power than the lasers in supermarket scanners and CD players. Researchers from corporate, university and government labs are eager to use the Jefferson lab laser to probe and manipulate the surfaces of a wide range of materials.

The research already under way could lead to some novel products, lab officials say, including bacteria-resistant nylon packaging, polyester that "feels" more like cotton, more corrosion-resistant turbine blades for power plants and lightweight structural material for use in "solar sails" for the propulsion of interplanetary spacecraft.

While the managers of the Jefferson facility - which is funded by the U.S. Department of Energy - were confident that a powerful free-electron laser would have real-world appeal, they sought state and corporate support before expanding beyond the lab's primary mission of basic nuclear research.

Future users were involved from the outset in building the laser facility and planning the research program, a change from past practice at some government-run labs. "In the 1990s, you have to be more customer-oriented," said Fred Dylla, manager of the lab's free-electron laser program. While the state of Virginia and the Energy Department paid much of the initial construction cost for the $34 million machine, corporations - including Northrop Grumman, DuPont and Armco - have contributed experimental equipment and will help pay operating costs for the laser.

The Navy will invest $10 million toward a three-year, $15-million upgrade of the laser. The Navy is interested in developing compact free-electron lasers that could be mounted on ships to disrupt the homing devices on hostile cruise missiles. The upgrade is expected to make the Jefferson laser at least 10 times more powerful.

While free-electron lasers have been around for two decades, they've had a checkered history. During the 1980s, the Reagan administration backed research on such lasers as one possible means for destroying enemy missiles. While much money was spent, Dylla said, few test devices were built.

But scientists were impressed with the potential of the free-electron laser, particularly because it could be "tuned" to produce a broad range of desired wavelengths of light. In a conventional chemical laser, the electrons in a medium - a gas, liquid or solid - are jostled with energy, causing them to jump to an excited state. When they decay to a lower energy level, they emit photons of light that can, in turn, stimulate additional emission of coherent light of the same wavelength.

In the Jefferson laser, the electrons are not tied to a particular chemical medium and a specific wavelength. They are stripped free of their host atoms, shot out of an electron gun in a continuous stream and accelerated to high speed. They pass through a "wiggler" - a series of magnets - that can "tune" the photon emissions to whatever wavelength of light the researcher desires.

That flexibility allows use of the laser for a broad range of experiments.

Also, the continuous nature of the originating electron beam means the laser can stay on 100 percent of the time instead of the intermittent output of other free-electron lasers. And the Jefferson laser is designed so that a substantial portion of the energy that is not converted to useful light during its first pass through the device can be recycled. That reduces operating costs, Dylla said, and is another reason why the Jefferson design is attracting the interest of industry.